The introduction of a drug into an intravenously, medically acceptable fluid is commonly done in clinical practice. Presently a beneficial drug is administered intravenously by one of the following procedures: (a) temporarily halting the flow of medical fluid and intravenously administering a solution of a drug to a patient through an injection port in an administration set, followed by resumption of administration of the medical fluid into the patients; (b) adding a drug to fluid inside a container, or into a volume control chamber in series with an administration set, which drug is carried by the flow of fluid into a patient; (c) introducing a drug into a piggyback container that is connected in tributary fashion to an administration set; or, (d) administering a drug by a pump that operates by one of various recognized pumping actions for producing flow, which flow of fluid containing a drug is pumped into a flow path, such as an indwelling catheter that enters the patient.
While these interior oriented techniques are used widely, they have certain disadvantages. For example, (e) the administration of a drug through repeated injections into an administration set is inconvenient and each time it is done it represents a break in sterility; (f) the use of pumps is expensive and inconvenient because of their size and weight; (g) the rate of drug delivery to a patient is dependent on internal fluid flow with all currently practiced means of drug infusion and, accordingly, it lacks drug delivery device control; (h) because of the relative chemical instability of medical solutions containing a drug, the administration of the drug often requires solubilization of the drug by the hospital pharmacists, or by the nurse at a time proximate to its administration; and (i) while it is current practice to give some drugs by brief infusions, typically of 30 to 120 minute duration repeated 3 or 4 times a day, it does not provide a means for carefully regulating the dose administered at any preselected time.